1. Field of the Invention
This invention pertains to the art of fluid conditioning apparatus, systems and methods, and is more particularly concerned with improved elastic fluid conditioning apparatus, systems and methods, such as those required to meet the physiological air requirements of passenger aircraft, although not limited thereto since the concept may be employed in other areas of the art.
2. Description of the Prior Art
The most typical exposition of the prior art is to be found in two applications for Letters Patent, one of which is No. 921,660, filed July 3, 1978, on an invention by Carl D. Campbell, and entitled "Fluid Conditioning System and Apparatus" now U.S. Pat. No. 4,198,830 dated Apr. 22, 1980. The other is No. 955,273, filed Oct. 26, 1978 on an invention by Alexander Anderson entitled "Heat Exchanger",now U.S. Pat. No. 4,246,963 issued Jan. 27, 1981. Both said applications are assigned to the same assignee as that of the present application.
Briefly stated, the disclosure of the Campbell application is directed to apparatus and a system in which fluid to be conditioned is admitted to first passageways of a heat exchanger and thereafter to a point of use, traversing flow conducting means which include the second passageways of a heat exchanger and fluid conditioning means which reduces the energy level of the fluid admitted to the second passageways below the energy level of the fluid admitted to the first passageways so as to increase the energy level of the fluid flowing through the second passageways by heat exchange with the fluid flowing through the first passageways.
The Campbell apparatus and system provides a very distinctive feature in the case of pressurized elastic fluids, in that moisture or other condensation entrained in the fluid in evaporated or mist form at the source, is readily condensed while the fluid is still in pressurized condition, and thus removable by a condensate separator without the requirement for a coalescer bag which is a source of a serious maintenance problem in the case of aircraft. The apparatus proved to be highly successful in removal of a very substantial portion of water from aircraft ventilation air conditioning systems.
One nuisance problem introduced by the component arrangement of the Campbell invention, when operating under some extreme conditions, occurred at the entrance to the last heat exchanger passageways in the flow path between the expansion turbine and the point of use. Over a period of operating time, ice would build up on the header bar and tend to block the flow of working fluid. It was deduced that although the upstream water separator removed substantially all of the air moisture, the remaining moisture would be transformed into ice particles or snow in the expansion turbine, and which would gradually accumulate and build up as ice at the header bars at the inlets of those last heat exchanger passageways. It was then conceived as disclosed in the aforesaid Anderson application, that if the header bars were provided with heater means, the accretion of the ice thereat would be prevented.
In connection with the present invention, it was conceived also that the air compressor discharge would provide an ideal source of heat which would then entail a minimum penalty to the system since only modest amounts of heat would be needed. Accordingly, the arrangement conceived resulted in the aforesaid Anderson invention.
Both said Campbell and Anderson inventions have proven to have important utility in applications to present day aircraft. However, the industry is highly competitive and cost conscious from standpoints of both initial capital investment and ongoing operating and maintenance expenditures. Hence in assessing the requirements for the next generation transport aircraft a very important factor considered by airframe manufacturers is the aircraft fuel penalty of the various systems and subsystems comprised in the final design. This is particularly so because of the present energy crisis coupled with the increasingly high cost of the fuel required in all phases of aircraft preparation for flight and the flight itself.
With this in mind, the inventors of the apparatus and system of the present application reasoned that the Campbell and Anderson inventions would form the most logical basis upon which to develop improvements to achieve the economies desired in the areas of fuel usage and maintenance costs without incurring penalties in other areas. As will be seen below the target was achieved by examining the following equation which forms the basis for calculating cabin refrigeration capacity: ##EQU1## wherein: Q=refrigeration capacity in BTU/per minute
W.sub.1 =flow rate into the cabin in pounds per minute PA1 C.sub.p =specific heat of the air (about 0.24 at 40.degree. F.) PA1 T.sub.cabin =the temperature desired for the cabin (.degree.F.) PA1 T.sub.1 supply=temperature of the air supplied from the system (.degree.F.) PA1 W.sub.2 =flow rate into the cabin in pounds per minute PA1 T.sub.2 supply=temperature of the air supplied from the system (.degree.F.)
Briefly stated, the problem is to lower the temperature T.sub.2 to a significant figure below T.sub.1, from which W.sub.2 can be reduced significantly below W.sub.1.